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    <script>
        const myFil = (ary) => {
            return ary.filter(item => item.a != "3")
                .map(item => item.a)
                .reduce((item, index) => item + "" + index)
        }
        console.log(myFil([{ a: '2' }, { a: '3' }, { a: '5' }, { a: '7' }]));

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